Information is extremely valuable for modern development and progress, especially in the development of new technology. However, many ways of storing and preserving information do not allow easy access to it. For example, information may be stored in library books, but identifying and obtaining the correct book often requires significant effort. Costs associated with accessing stored information may reduce the effective value of the information.
Many developing technologies have been embraced because they increase accessibility to information. Microfilm, magnetic tapes, magnetic disk media, optical disk media, and non-volatile integrated memories are examples of technologies that have increased accessibility to information stored on them. Non-volatile integrated memories are of particular interest here.
Integrated memories are electrical circuits that are configured to store information in digital form. This digital information, or “data,” is readily accessible to a digital device appropriately coupled to the integrated memory. Depending on the particular technology employed, data can be accessed at truly astonishing rates.
Not all integrated memories are non-volatile. Volatile integrated memories suffer loss of stored data in the absence of electrical power. In the past, this shortcoming has been offset by the high rate of access to the data.
Magnetic integrated memories, as that term is used herein, are integrated memories that use magnetization states to store data. Magnetic materials can be given magnetization states (e.g., magnetic orientations) that do not rely on the continued presence of electrical power to preserve the magnetization state. A variety of sensing techniques may be employed to detect magnetization states in these memories and to determine the data these states represent.
One issue with the current technology for these memories is non-uniformity. A given portion of a magnetic integrated memory may have characteristics that vary from another portion of the memory. These characteristics may relate to the strength of the stored magnetization and to the sensitivity of sensing configurations. Accordingly, a sense signal that indicates stored magnetization characteristics is expected to exhibit position-dependent variation.
One proposed method for dealing with the position-dependent variation makes use of the reproducibility of the variation. The proposed method involves multiple measurements: a measurement of the original sense signal associated with a storage location; and a measurement of the original sense signal after known data value is placed in the storage location. This second measurement is repeated for each possible data value. The known data value having a sense signal “closest” to the original sense signal is identified as the stored data value.
Because this method involves replacing the originally stored data with known data, it is often called a “destructive read.” Destructive read methods require numerous operations on the storage location. A read method that accommodates position-dependent variation while requiring fewer operations may offer higher access rates.